It has been proved by many related researches since 1990s that micro or nano scale zero-valent iron (ZVI) is a very effective material for soil and groundwater remediation. Contaminants such as chlorinated volatile organic compounds, heavy metals, pesticides, PCBs and dioxins can be degraded by ZVI. Nano-scale ZVI can react faster due to smaller particle size and larger surface area. However, the bare nanoscale ZVI is also easy to be corroded, which thus shortens its longevity. Currently, ZVI's applications are still restricted in the groundwater environment where is a hypoxic or anoxic condition. It is barely seen that ZVI is applied to water or wastewater treatment system that might be due to the higher cost, higher water chroma and turbidity, difficult recycling and separation, and so on. On the other hand, ZVI has the characteristics of hydrogen production and magnetism, which is not yet fully developed.
Zero-valent metals (ZVMs), for example, ZVI (Fe0), zero-valent zinc (Zn0) and zero-valent aluminum (Al0), have excellent reduction ability to decompose water and generate hydrogen. For the commonly-used slurry type of ZVM, the generated hydrogen is usually mixed with ZVM powders in the slurry and thus is hard to be used more efficiently. Moreover, ZVM powders relatively have more surface areas exposed to air, that may shorten the longevity and increase the cost.
It has been shown that the ZVM powders can be coated with organic substances (for example, polymers and surfactants) or inorganic substances (for example, silicon dioxide and titanium dioxide) to slow down the corrosion rate and to increase reaction rate. However, that still cannot extend the ZVM materials into various application fields.
Therefore, it should be necessary to provide a better method for manufacturing zero-valent metals, which strengthens the original features and produces more industrial applications of ZVMs.